Detergent compositions are required to have various functions such as emulsifying or solubilizing actions on dirt components such as oil, and detergency. Among them, detergents for the skin, hair or dishes treated directly by human hands are required to have an improved feeling upon use during cleansing (good foamability and foam quality), during rinsing, and after drying, as opposed to industrial detergents used for metal cleansing.
For skin, hair or dish detergent compositions, therefore, various sorts of surfactants and feel-improving agents are used to enhance their foamability and improve a feeling upon use, respectively. In particular, when a cationic polymer is incorporated in a detergent for the skin or hair, it exhibits an excellent feel-improving function and therefore is used widely. On the other hand, a detergent composition containing a large amount of a cationic polymer has such a problem that its foamability fades away, and as a result, could lead to the deteriorative feeling upon use. This method is not constraint-free, as such.
A cationic polymer is usually provided in powder form so that (1) much time and labor must be spent for solubilizing it, (2) its handling ability is not so good due to solidification (blocking) caused by moisture absorption, and (3) dust generated from the powder worsens the working environment. With a view to overcoming these problems, a cationic polymer is used in the form of an aqueous solution. However, a high-molecular-weight cationic polymer having a good performance as a feel-improving agent tends to become highly viscous, thus making it impossible for the aqueous solution to be obtained in high concentration. The aqueous solution of a cationic polymer is therefore not useful from the standpoint of economy, for example, a transportation cost. Furthermore, the acceptable amount of a cationic polymer that can be added to a detergent composition is limited.
As a method of raising the concentration of a cationic polymer, replacement of a portion or whole of the aqueous solution with an organic solvent or oil component or emulsification of the aqueous solution is known. However, when added to a detergent composition, such an ingredient not only could cause a drastic reduction in foamability, but such an emulsion also has a problem with the composition stability.
As a method requiring no solvent, on the other hand, Patent Document 1 describes a method of using a specific cationic polymer in combination with an inorganic salt and Patent Document 2 describes a method of modifying a cationic polymer with an acid. These methods, however, cannot overcome the problem of reduction in foamability caused by the addition of a cationic polymer. Further, the addition of an inorganic salt or modification with an acid deteriorates the performance of the cationic polymer. Patent Document 3 discloses an example of adding a cationic polymer in high concentration while using a nonionic surfactant having an HLB of 12 or greater in combination. This method requires the additional use of a propellant for foaming. What is worse, this type of composition cannot generate sufficient foamability even if incorporated in a detergent.
Thus, from none of the prior art is it known to be able to obtain a detergent composition that is capable of containing therein a cationic polymer in high concentration and impairing neither foamability of the detergent nor feeling upon use even when incorporated in a detergent.
[Patent Document 1] JP-A-06-329866
[Patent Document 2] JP-A-10-7808
[Patent Document 3] WO96/32093